IEC TR 61282-16:2022

IEC TR 61282-16 ®
Edition 1.0 2022-05
TECHNICAL
REPORT
Fibre optic communication system design guidelines –
Part 16: Coherent receivers and transmitters with high-speed digital signal
processing
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IEC TR 61282-16 ®
Edition 1.0 2022-05
TECHNICAL
REPORT
Fibre optic communication system design guidelines –

Part 16: Coherent receivers and transmitters with high-speed digital signal

processing
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.01 ISBN 978-2-8322-0094-0

– 2 – IEC TR 61282-16:2022  IEC 2022
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 9
4 Background . 12
5 Coherent transmission of vector-modulated signals . 13
5.1 Typical receiver architecture . 13
5.2 Typical transmitter architecture . 14
5.3 Vector-modulated signals . 15
5.3.1 Mathematical description . 15
5.3.2 Binary amplitude and phase modulation . 16
5.3.3 Quadrature amplitude modulation . 17
5.3.4 Polarization multiplexing . 18
5.3.5 Higher-dimensional coding and constellation shaping . 18
6 Coherent receiver architectures and functional capabilities . 19
6.1 Basic principle of coherent detection . 19
6.1.1 General . 19
6.1.2 Homodyne and heterodyne detection . 19
6.1.3 Intradyne detection . 21
6.1.4 Polarization dependence . 21
6.1.5 Frequency dependence . 22
6.1.6 Phase and polarization diversity . 22
6.2 Single coherent mixer with balanced detection . 23
6.2.1 Principle of operation . 23
6.2.2 Common-mode rejection . 24
6.2.3 Polarization dependence . 26
6.2.4 Homodyne detection . 27
6.2.5 Heterodyne detection . 28
6.3 Dual coherent mixer with phase diversity . 29
6.3.1 Principle of operation . 29
6.3.2 Intradyne detection with frequency offset removal. 31
6.3.3 Compensation of chromatic dispersion. 33
6.3.4 Compensation of I-Q skew and phase offset . 40
6.3.5 Spectral shaping and frequency equalization . 42
6.4 Quadruple mixer with phase and polarization diversity . 46
6.4.1 Principle of operation . 46
6.4.2 Polarization demultiplexing . 48
6.4.3 Compensation of polarization-mode dispersion . 51
6.4.4 Compensation of polarization-dependent loss and residual CD . 53
6.4.5 Carrier phase recovery . 54
6.4.6 Impact of laser phase noise . 55
6.5 High-resolution spectral analysis with coherent receivers . 62
6.5.1 Measurement methods . 62

6.5.2 Dual mixer with polarization diversity . 63
6.5.3 Examples of high-resolution spectral analysis . 64
7 Digital signal processing in coherent receivers . 66
7.1 Basic features of digital signal processing . 66
7.2 Real-time DSPs for fibre optic communication systems . 70
7.2.1 Basic functions . 70
7.2.2 Timing recovery . 71
7.2.3 Cycle slip detection . 71
7.2.4 Compensation of nonlinear transmission effects . 71
7.2.5 FEC decoding and performance monitoring . 72
7.3 Software-based DSPs for optical modulation analysers . 73
8 Transmitters for vector-modulated signals . 75
8.1 Generation of vector-modulated signals . 75
8.2 Single Mach-Zehnder modulator . 77
8.2.1 Principle of operation . 77
8.2.2 Modulator extinction ratio . 81
8.2.3 Adaptive bias control in Mach-Zehnder modulators . 83
8.3 Dual Mach-Zehnder modulators . 85
8.3.1 Quadrature-amplitude modulation . 85
8.3.2 Compensation of finite extinction ratio . 86
8.3.3 Adaptive control of I-Q phase . 87
8.4 Quadruple modulators for polarization-multiplexed signals . 91
9 Digital signal processing in transmitters for vector-modulated signals . 94
9.1 Pre-distortion of optical signals . 94
9.1.1 General . 94
9.1.2 Pre-compensation of linear transmitter impairments. 95
9.1.3 Determination of transmitter frequency response . 96
9.1.4 Determination of transmitter skew . 101
9.1.5 Pre-compensation of modulator nonlinearity . 103
9.2 Symbol mapper, FEC encoding and framing . 105
10 Implementation and typical performance specifications . 106
10.1 Coherent receiver . 106
10.1.1 Implementation . 106
10.1.2 Typical performance specifications . 107
10.2 Optical transmitter . 108
10.2.1 Implementation . 108
10.2.2 Typical performance specifications . 109
10.3 Integrated coherent receiver and transmitter . 111
10.4 Tuneable laser assemblies . 111
10.4.1 Implementation . 111
10.4.2 Typical performance specifications . 111
Bibliography . 113

Figure 1 – Coherent optical receiver . 13
Figure 2 – Optical transmitter for coherent transmission . 14
Figure 3 – Generation of vector modulated signals . 16
Figure 4 – Examples of modulation formats for coherent communication . 17
Figure 5 – Signal and local oscillator frequencies for homodyne detection . 20

– 4 – IEC TR 61282-16:2022  IEC 2022
Figure 6 – Signal and local oscillator frequencies for heterodyne detection . 20
Figure 7 – Electrical spectra of homodyne and heterodyne beat signals . 21
Figure 8 – Single balanced mixer for coherent reception . 24
Figure 9 – Balanced heterodyne mixer with electrical down-mixing . 28
Figure 10 – Dual coherent mixer with phase diversity . 30
Figure 11 – Intradyne beat spectrum with 2 GHz frequency offset . 32
Figure 12 – Differential phase shifts introduced by 3 000 ps/nm GVD .
...